1 The Little Desert Planet 1

2 Image Credit: meridiangraphics.netmeridiangraphics.net Mythology 2

3 Mars Mythology (Greek & Roman) Son of Zeus (Jupiter) & Hera (Juno) Grandson of Cronos (Saturn) Half-brother to Hercules & Orion Considered to be father of Romulus & Remus, founders of Rome, by the Romans. 3

4 Mars Mythology (Greek & Roman) The ancient Greeks believed him to be the father of Phobos (Fear) and Deimos (Panic). Aphrodite (Venus) was their mother. –‘Phobos’ gives us our word ‘phobia’. –‘Deimos’ gives us our words demon & demonic. Mars (Ares) was, ironically, the patron god of both warfare and agriculture! Image Credit: plantpath.ifas.ufl.edu/ 4

5 Mars’ Physical Properties Mars is roughly ½ of Earth’s diameter. Image Credit: rst.gsfc.nasa.gov/Sect19/ br_earth-mars-front.jpg 5

6 Mars has a mass about 11% that of the Earth. The Earth is 9.3 x heavier! Image: 6

7 Mars’ density is 3.94 g/cm 3. Earth’s is 5.5 g/cm 3. ?????? Image Credit: 7

8 Conclusion: Mars’ core is proportionately smaller than Earth’s core. Image credit: 8

9 Orbit & Rotation Not Too Different From Ours Average distance from the sun: 228 million km (1.52 A.U.) Perihelion: 207 million km. Aphelion: 249 million km. Orbit eccentricity: (very elliptical) 9

10 Familiar Orbit Orbital period: 687 days or 1.88 years Inclination of orbit to ecliptic: 1.85 o –This is enough to be noticeable to the naked eye. Minimum distance from earth is 55 million km, at opposition. Maximum is 401 million km, at superior conjunction. 10

11 Familiar Orbit Due to the 1.88 year orbit, seasons on Mars would last about 5½ months on average! But…the Martian summer is over a month longer than the winter, due to Mars’ elliptical orbit! 11

12 The 2003 opposition was here 12

13 Familiar Rotation Mars rotates in the normal (prograde) direction in 24 hours 37 minutes. (Sidereal period) Its noon-to-noon day is 24 hours 40 minutes. (Synodic period) Axis is tilted 25.2 o relative to its orbit. Fast rotation, yet no magnetic field. –Conclusion? 13

14 Mars’ Interior Our conclusion may be wrong! "Mars is influenced by the gravitational pull of the Sun. This causes a solid body tide with a bulge toward and away from the Sun (similar in concept to the tides on Earth). However, for Mars this bulge is much smaller, less than 1 centimeter (0.4 inch). By measuring this bulge in the Mars gravity field we can determine how flexible Mars is. The size of the measured tide is large enough to indicate the core of Mars can not be solid iron but must be at least partially liquid." (Dr. Charles Yoder – JPL Planetary Sci.) 14

15 Almost no magnetic field Mars has no internally-produced magnetic field (no internal dynamo), even though it rotates almost as fast as earth does. Solar wind interacts with the thin atmosphere to produce an ionosphere, which produces an induced magnetosphere. The bow shock is located only ¼ of a Martian diameter out from the surface (1700 km). 15

16 Strength is 1/10,000 th of earth’s field. 16

17 Mars’ magnetic field What little bit of magnetism Mars does have is broken up into small regions – it’s not planet-wide like the earth’s. If the interior of Mars is still at least partly molten, and Mars rotates fast, why no magnetic field? Hmmmm……..!? 17

18 photojournal.jpl.nasa.gov 18

19 What does this mean for colonization of Mars? 19

20 In the late 1800’s, an Italian astronomer, Giovanni Schiaparelli, thought he saw long straight “canali” or channels on Mars. He drew his observations…….. phys-astro.sonoma.edu 20

21 Schiaparelli didn’t make any claims about what these channels were…but someone else did. 21

22 Percival Lowell Wealthy American Astronomer Percival Lowell mistook the Italian word “canali” to mean “canals”. (Maybe a natural mistake!) He used his own money to build the Lowell Observatory near Flagstaff, Arizona, to study these “canals”. Lowell concluded that these “canals” had been built by intelligent “Martians”. 22

Lowell at his telescope. 23

24 Lowell’s observatory and telescope. 24

25 Lowell’s legacy lives! Lowell’s idea about intelligent Martians became very popular with the American public. Much of our early (and present) science fiction comes from this idea. H.G. Wells’ “War of the Worlds” was based upon this idea. 25

26

27 The War of the Worlds drzeus.best.vwh.net/ wotw/illus/interior.html 27

monsters/70.html 28

29 “This is Glub, sitting in for Tom Dunn on the ‘Eleven O’Clock News,’ and I wish to announce that there has been a rather sudden and sweeping change in your government. 29

30 We still have little green men – a coincidence? 30